The invention addresses two different and independent difficulties in the art of liquid chromatography.
Firstly, there is a lack of robust stationary phases for high performance liquid chromatography (HPLC) that provide broadly useful retention and separation patterns. Benefiting from the superior hydraulic and mass transfer kinetic properties of a monolithic structure, a variety of monolithic columns have been developed for fast separations during the last few years. These well known monolithic columns are categorized in to two general groups: silica-based columns and polymeric columns. Silica-based stationary phases are generally feasible only with mobile phases having a pH in the range of 3 to 10. Moreover, although polymeric phases are not as pH-limited, they are often degraded rapidly when used with certain common organic solvents and/or at high temperatures. Thus, there is a need for a rugged monolithic column made with a stationary phase that can be used in a wide range of chemical environments and at elevated temperatures.
Electrochemically modulated liquid chromatography (EMLC) requires an electrically conductive stationary phase, which generally excludes all silica-based and most polymeric stationary phases. Carbon-based particulate stationary phases are currently the only type of stationary phases used for EMLC. Conventional beds packed with porous graphite particles suffer from a poor electrical conductivity, hence from a heterogeneous distribution of the electric charges of the particles. The electrical equilibrium of the column can only be achieved after washing it for a very long time with the mobile phase. This causes a slow adjustment of the experimental conditions and the waste of valuable chemicals. The development of EMLC has been considerably slowed down by the lack of a suitable stationary phase.
Carbon monoliths having hierarchical porosity have been made using a silica monolith having hierarchical porosity as a template. Carbon monoliths made thereby take the shape of the voids (pores) of the template and are of very low density and are not structurally robust. Such carbon monoliths are known to undergo structural collapse under an electron beam of an electron microscope. A robust carbon monolith having hierarchical porosity is needed for applications such as chromatography and other chemical separations.